One-time-programmable (OTP) memory is memory that may be programmed to a specific value only once and thereafter may not be changed. OTP memory is typically implemented as erasable programmable read only memory (EPROM) but packaged in such way so that ultra-violet light may not be used to erase contents of the EPROM.
OTP memory is often utilized in, for example, electronic devices such as cell phones, personal digital assistants (PDA), and cameras. These electronic devices all contain stored information that may be utilized for device configuration and to control certain operating modes and/or functions. In order to facilitate proper operation of these operating modes and/or functions, it is critical that stored information is not tampered with. For example, during a power ON sequence, various device register locations in a cell phone have to be read and/or written in order for the phone to power up and enter a standby mode. Similarly, when a PDA is powered ON, one or more register locations in the PDA may be read and/or written in order for the PDA to display a user programmed or default display screen and wait for a user input.
In some conventional systems, configuration information may be stored in read-only memory (ROM). However, in instances where ROM is utilized, if a change is required, the ROM has to be updated and this may entail physically removing and replacing the ROM device. Accordingly, a ROM based solution is not appropriate when information has to be programmed.
In certain instances, it may be desirable to utilize a programmable memory in which one or more memory locations may be written only once. In this regard, a one-time programmable (OTP) memory may be utilized to provide additional security for the data stored in an OTP memory. Once a bit in an OTP memory is programmed, for example, from a binary zero to a binary one, then that particular bit typically cannot be programmed again.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.